A capillary pumped diphasic fluid loop, often by misuse of language simply called a “fluid loop”, is a system that conveys thermal energy from a hot source to a cold source, by using capillarity as the driving pressure, and the (liquid-vapour) phase change is used as a means of conveying energy.
Such a fluid loop generally comprises an evaporator intended to extract heat from a hot source and a condenser intended to return this heat to a cold source. The evaporator and the condenser are linked by a pipe, called a liquid pipe, in which a cooling fluid circulates for the most part in the liquid state in the cold part of the fluid loop, and a pipe, called a vapour pipe, in which the same cooling fluid circulates for the most part in the gaseous state in its hot portion. The various pipes are in the form of tubing elements, generally made of metal (for example made of stainless steel or aluminium) typically having a diameter of a few millimeters. The evaporator comprises a housing containing a capillary structure providing the pumping of the cooling fluid in the liquid phase by capillarity.
The use of a system constituted by at least two fluid loops for cooling a hot source is known. The evaporators of the two fluid loops are both positioned in heat exchange with the hot source, at a distance from each other which can vary from a few centimeters to typically a meter. Such a system can also comprise more than two fluid loops and in particular two groups of fluid loops. In a variant, such a system is suitable for cooling one or more hot sources arranged in different places.
In a first mode of operation of this system, it is desirable that a single fluid loop, called main fluid loop, functions to remove heat from the hot source, the other fluid loop being idle and only starting in the event of a breakdown of the main fluid loop. This mode of operation is generally called “cold redundancy” of the fluid loops.
However, on starting the two fluid loop system, when the temperature of the hot source increases and delivers its thermal power, sometimes both fluid loops start, as each one receives a portion of this thermal energy.
In a second mode of operation of this system, it is desirable for both fluid loops to operate at the same time in order to remove the heat from the hot source. This mode of operation is generally called “hot redundancy” of the fluid loops.
In many cases, on starting the two fluid loop system, only one of the two fluid loops starts, the other fluid loop remaining permanently idle. This manner of operation limits by half the thermal performance of the heat transfer system.
In order to resolve these control difficulties of the two-loop system, it is known, in particular from document EP 2032440, to reduce or stop the transportation capacity of a fluid loop and therefore its thermal performance by heating the cooling fluid situated in its housing, for example by means of a heater or a passive system using a thermal capacity. In this case, a heating power of the housing of approximately a few percent of the thermal power of the fluid loop is sufficient to stop the fluid loop.
It is also known that cooling the housing of the fluid loop promotes the starting of the latter. This cooling can be obtained according to the state of the art by using a cooling element based on the Peltier effect.
However, these solutions are complex to implement due to the use of heaters and/or coolers, temperature sensors and a control logic. Moreover, these solutions require a certain heating power, typically from a few watts to a few tens of watts for fluid loops of 10 to 1000 W power.
A purpose of the present invention is in particular to overcome these drawbacks.